No RIN obtained with Bioanalyzer?

I ran some samples (I used RNAlater when dissecting the CA1 out of the hippocampus in the brain). I get a small 28s peak, but not super small. And there aren't peaks between 18s and 28s. It doesn't look degraded judging by the histogram(?the plot's called a histogram?).

I've seen plots before with really bad 28s peaks and they had RIN values. But none of my samples had RIN values? They were all 'N/A'. How come it can't generate RINs for me? Has anyone ever seen this before?

maybe it's the marker problem. Normally in each of your samples, you'll need to add something (like a spike in control) and after running, the spike-in thingy will align with your ladder and that's how Bioanalyzer calculate the size of your peaks, the area under the peak etc etc and finally come out with the ratio and RIN.
If the Bioanalyzer couldn't find the spike in marker to align with the ladder, it will not be able to calculate any RIN.